U.S. patent application number 11/138525 was filed with the patent office on 2005-10-06 for methods of synthesis of polysuccinimide, copolymers of polysuccinimide and derivatives thereof.
Invention is credited to Redlich, George H., Swift, Graham.
Application Number | 20050222378 11/138525 |
Document ID | / |
Family ID | 34423415 |
Filed Date | 2005-10-06 |
United States Patent
Application |
20050222378 |
Kind Code |
A1 |
Swift, Graham ; et
al. |
October 6, 2005 |
Methods of synthesis of polysuccinimide, copolymers of
polysuccinimide and derivatives thereof
Abstract
Disclosed are methods of synthesis of polysuccinimide,
copolymers and derivatives thereof: also disclosed are methods of
forming derivatives by ring-opening initiation reactions.
Inventors: |
Swift, Graham; (Chapel Hill,
NC) ; Redlich, George H.; (East Norriton,
PA) |
Correspondence
Address: |
STAMATIOS MYLONAKIS
7009 CASHELL MANOR COURT
DERWOOD
MD
20855-1201
US
|
Family ID: |
34423415 |
Appl. No.: |
11/138525 |
Filed: |
May 27, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11138525 |
May 27, 2005 |
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10698411 |
Nov 3, 2003 |
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6903181 |
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10698411 |
Nov 3, 2003 |
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10307349 |
Dec 2, 2002 |
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6686440 |
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10698411 |
Nov 3, 2003 |
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10307387 |
Dec 2, 2002 |
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6686441 |
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10307349 |
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09776897 |
Feb 6, 2001 |
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6495658 |
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Current U.S.
Class: |
528/328 |
Current CPC
Class: |
Y02P 20/54 20151101;
C08G 73/1092 20130101; C07C 227/40 20130101; C08L 79/08 20130101;
C07C 227/40 20130101; C07C 229/24 20130101 |
Class at
Publication: |
528/328 |
International
Class: |
C08G 069/10 |
Claims
1. A method for preparing a polysuccinimide derivative, which
comprises, subjecting the polysuccinimide to a ring-opening
reaction.
2. The method of claim 1, wherein said polysuccinimide is formed by
polymerization of L-aspartic acid in a supercritical fluid.
3. The method of claim 1, wherein said ring-opening reaction is
carried out in a supercritical fluid.
4. The method of claim 1, wherein said ring-opening reaction is
carried out subsequently to the formation of polysuccinimide in a
supercritical fluid.
5. The method of claim 1, wherein said ring-opening reaction is
carried out in water.
6. The method of claim 1, wherein said ring-opening reaction is
carried out in the presence of an amine.
7. The method of claim 6, further comprising water as a
cosolvent.
8. The method of claim 7, wherein said amine is a combination of
amines.
9. The method of claim 8, wherein said combination of amines is
comprised of ammonium hydroxide and 2-aminoethanol to form a
resin.
10. The method of claim 9, wherein said resin contains a free
carboxylic acid salt and the amides of ammonia and
aminoethanol.
11. The method of claim 6, wherein said amine has the general
formula: R.sub.1R.sub.2R.sub.3N; where R.sub.1, R.sub.2, and
R.sub.3 are the same or different radicals selected from the group
consisting of hydrogen, an alkyl, a substituted alkyl, an alkenyl,
an aryl, an aryl-alkyl, and a substituted aryl radical.
12. The method of claim 11, wherein said alkyl is selected from the
group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl,
isobutyl, sec-butyl, t-butyl, n-amyl, isoamyl, t-amyl, n-hexyl,
n-octyl, capril, n-decyl, lauryl, myristyl, cetyl, and stearyl.
13. The method of claim 11, wherein said substituted alkyl is
hydroxyethyl.
14. The method of claim 11, wherein said alkenyl is allyl.
15. The method of claim 11, wherein said aryl is phenyl.
16. The method of claim 11, wherein said aryl-alkyl is benzyl.
17. The method of claim 11, wherein said substituted aryl radical
is selected from the group consisting of alkylphenyl, chlorophenyl
and nitrophenyl.
18. The method of claim 6, wherein said amine is triethanol
amine.
19. The method of claim 6, wherein said amine is selected from the
group consisting of aminopyrdine, imidazole and a polyamine.
20. The method of claim 19, wherein said polyamine is selected from
the group consisting of a gelatin, chitin, lysine, ornithine and
melamine.
Description
[0001] This application is a Continuation of application Ser. No.
10/698,411, filed Nov. 03, 2003, which is a Continuation-In-Part of
application Ser. Nos. 10/307,349 and 10/307,387, both filed Dec. 2,
2002, which are a Continuation and Continuation-In-Part,
respectively, of application Ser. No. 09/776,897, filed Feb. 6,
2001, now U.S. Pat. No. 6,495,658, issued Dec. 17, 2002, all three
of which are incorporated herein by reference in their
entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a process for the
preparation of polysuccinimide, and derivatives; the
polysuccinimide is formed in a supercritical fluid (SCF), such as
liquid CO.sub.2 or supercritical CO.sub.2 in an organic cosolvent,
starting with L-aspartic acid, and the derivatives are formed by a
ring-opening reaction.
[0004] 2. Discussion of the Related Art
[0005] L-Aspartic acid has been produced commercially since the
1980's via immobilized enzyme methods. The aspartic acid so
produced mainly has been used as a component of the synthetic
sweetener, N-aspartyl phenylalanine methyl ester
(ASPARTAME.RTM.).
[0006] In a typical production pathway, a solution of ammonium
maleate is converted to fumarate via action of an immobilized
enzyme, maleate isomerase, by continuous flow over an immobilized
enzyme bed. Next, the solution of ammonium fumarate is treated with
ammonia also by continuous flow of the solution over a bed of the
immobilized enzyme, aspartase. A relatively concentrated solution
of ammonium asparate is produced, which then is treated with an
acid, for example nitric acid, to precipitate aspartic acid. After
drying, the resultant product of the process is powdered or
crystalline L-aspartic acid. Prior art that exemplifies this
production pathway includes U.S. Pat. No. 4,560,653 to Sherwin and
Blouin (1985), U.S. Pat. No. 5,541,090 to Sakano et al. (1996), and
U.S. Pat. No. 5,741,681 to Kato et al. (1998).
[0007] In addition, non-enzymatic, chemical routes to D,L aspartic
acid via treatment of maleic acid, fumaric acid, or their mixtures
with ammonia at elevated temperature have been known for over 150
years (see Harada, K., Polycondensation of thermal precursors of
aspartic acid. Journal of Organic Chemistry 24, 1662-1666 (1959);
also, U.S. Pat. No. 5,872,285 to Mazo et al. (1999)). The above
chemical routes of maleic acid and ammonia are less sterically
controlled as well as less quantitative and the product is a D,L
racemic mixture. Although the non-enzymatic routines are
significantly less quantitative than the enzymatic syntheses of
aspartic acid, possibilities of continuous processes and recycling
of reactants and by-products via chemical routes are
envisioned.
[0008] Polymerization and copolymerization of L-aspartic acid alone
or with other comonomers is known. As reviewed in U.S. Pat. No.
5,981,691 to Sikes (1999), synthetic work with polyamino acids,
beginning with the homopolymer of aspartic acid, dates to the mid
1800's and has continued to the present. Interest in polyaspartates
and related molecules increased in the mid 1980's as awareness of
the commercial potential of these molecules grew. Particular
attention has been paid to biodegradable and environmentally
compatible polyaspartates for commodity uses such as detergent
additives and superabsorbent materials in disposable diapers,
although numerous other uses have been contemplated, ranging from
water-treatment additives for control of scale and corrosion to
anti-tartar agents in toothpastes.
[0009] There have been some teachings of producing copolymers of
succinimide and aspartic acid or aspartate via thermal
polymerization of maleic acid plus ammonia or ammonia compounds.
For example, U.S. Pat. No. 5,548,036 to Kroner et al. (1996) taught
that polymerization at less than 140.degree. C. resulted in
aspartic acid residue-containing polysuccinimides. However, the
reason that some aspartic acid residues persisted in the product
polymers was that the temperatures of polymerization were too low
to drive the reaction to completion, leading to inefficient
processes.
[0010] JP 8277329 (1996) to Tomida exemplified the thermal
polymerization of potassium asparate in the presence of 5 mole %
and 30 mole % phosphoric acid. The purpose of the phosphoric acid
was stated to serve as a catalyst so that molecules of higher
molecular weight might be produced. However, the products of the
reaction were of a lower molecular weight than were produced in the
absence of the phosphoric acid, indicating that there was no
catalytic effect. There was no mention of producing copolymers of
aspartate and succinimide; rather, there was mention of producing
only homopolymers of polyaspartate. In fact, addition of phosphoric
acid in this fashion to form a slurry or intimate mixture with the
powder of potassium aspartate, is actually counterproductive to
formation of copolymers containing succinimide and aspartic acid
residue units, or to formation of the condensation amide bonds of
the polymers in general. That is, although the phosphoric acid may
act to generate some fraction of residues as aspartic acid, it also
results in the occurrence of substantial amounts of phosphate anion
in the slurry of mixture. Upon drying to form the salt of the
intimate mixture, such anions bind ionically with the positively
charged amine groups of aspartic acid and aspartate residues,
blocking them from the polymerization reaction, thus resulting in
polymers of lower molecular weight in lower yield.
[0011] Earlier, U.S. Pat. No. 5,371,180 to Groth et al. (1994) had
demonstrated production of copolymers of succinimide and aspartate
by thermal treatment of maleic acid plus ammonium compounds in the
presence of alkaline carbonates. The invention involved an
alkaline, ring-opening environment of polymerization such that some
of the polymeric succinimide residues would be converted to the
ring-opened, aspartate form. For this reason, only alkaline
carbonates were taught and there was no mention of cations
functioning themselves in any way to prevent imide formation.
[0012] More recently, U.S. Pat. No. 5,936,121 to Gelosa et al.
(1999) taught formation of oligomers (Mw<1000) of aspartate
having chain-terminating residues of unsaturated dicarboxylic
compounds such as maleic and acrylic acids. These aspartic-rich
compounds were formed via thermal condensation of mixtures of
sodium salts of maleic acid plus ammonium/sodium maleic salts that
were dried from solutions of ammonium maleate to which NaOH had
been added. They were producing compounds to sequester
alkaline-earth metals. In addition, the compounds were shown to be
nontoxic and biodegradable by virtue of their aspartic acid
composition. Moreover, the compounds retained their
biodegradability by virtue of their very low Mw, notwithstanding
the presence of the chain-terminating residues, which when
polymerized with themselves to sizes about the oligomeric size,
resulted in non-degradable polymers.
[0013] A number of reports and patents in the area of polyaspartics
(i.e., poly(aspartic acid) or polyaspartate), polysuccinimides, and
their derivatives have appeared more recently. Notable among these,
for example, there have been disclosures of novel superabsorbents
(U.S. Pat. No. 5,955,549 to Chang and Swift, 1999; U.S. Pat. No.
6,027,804 to Chou et al., 2000), dye-leveling agents for textiles
(U.S. Pat. No. 5,902,357 to Riegels et al., 1999), and solvent-free
synthesis of sulfhydryl-containing corrosion and scale inhibitors
(EP 0 980 883 to Oda, 2000). There also has been teaching of
dye-transfer inhibitors prepared by nucleophilic addition of amino
compounds to polysuccinimide suspended in water (U.S. Pat. No.
5,639,832 to Kroner et al., 1997), which reactions are inefficient
due to the marked insolubility of polysuccinimide in water.
[0014] U.S. Pat. No. 5,981,691 to Sikes, et al purportedly
introduced the concept of mixed amide-imide, water-soluble
copolymers of aspartate and succinimide for a variety of uses. The
concept therein was that a monocationic salt of aspartate when
formed into a dry mixture with aspartic acid could be thermally
polymerized to produce the water-soluble copoly(aspartate,
succinimide). The theory was that the aspartic acid comonomer when
polymerized led to succinimide residues in the product polymer and
the monosodium aspartate comonomer led to aspartate residues in the
product polymer. It was not recognized that merely providing the
comonomers was not sufficient to obtain true copolymers and that
certain other conditions were necessary to avoid obtaining
primarily mixtures of polyaspartate and polysuccinimide copolymers.
In U.S. Pat. No. 5,981,691, the comonomeric mixtures were formed
from an aqueous slurry of aspartic acid, adjusted to specific
values of pH, followed by drying. There was no teaching of use of
solutions of ammonium aspartate or any other decomposable cation
plus NaOH, or other forms of sodium or other cations, for
generation of comonomeric compositions of aspartic acid and salts
of aspartate. Thus, although some of the U.S. Pat. No. 5,981,691
examples obtain products containing some copolymer in mixture with
other products, particularly homopolymers, as discussed in the
Summary of the Invention below, the theory that true copolymers
could be obtained merely by providing the comonomers in the manner
taught in U.S. Pat. No. 5,981,691 was not fully realized.
[0015] Thus, to date, there have been no successful disclosures of
water-soluble or wettable, mixed amide/imide polyamino acids such
as copolymers of aspartate and succinimide, related
imide-containing polyamino acids, polysuccinimide or derivatives
thereof.
SUMMARY OF THE INVENTION
[0016] One aspect of the invention relates to polymerizing aspartic
acid to polysuccinimide in a supercritical fluid (SCF), such as
liquid CO.sub.2 or supercritical CO.sub.2 in combination with an
organic cosolvent. In another aspect of the present invention
aspartic acid is polymerized in a supercritical fluid to form
copoly(succinimide, aspartarte). In yet another aspect of the
present invention the polysuccinimide or the copoly(succinimide,
aspartate) formed in the supercritical fluid is derivatized to
produce derivatives of the polysuccinimide and of the
copoly(succinimide, aspartate). In another aspect of the present
invention, the polysuccinimide or the copoly(succinimide,
aspartate) formed in a supercritical fluid are subsequently
isolated and melt processed. Dewatering stage or concentration of
monomers may be done by any suitable technique including wiping
film evaporator, drum drying, evaporation in a screw reactor or
inline concentrator, etc.
BRIEF DESCRIPTION OF THE DRAWING
[0017] FIG. 1 depicts a diagram of a typical extrusion machine. The
injection port allows the introduction of reactants into the
injection machine for post reactions of the polymer or copolymers
in the melt. The sections of the screw are separately heated and
interchangeable. Thus, the injection port can be placed downstream
in the injection machine depending on the required residence time
required for a desired reaction.
[0018] FIG. 2 is an FTIR spectrum of a sample treated with excess
triethanolamine. As seen in the spectrum there is no peak at 1710
wave numbers where the succinimide ring absorbs. The peak at 1577
is for the amide backbone, while the peak at 1386 is for the
carboxylate group. The strong peaks at 1030-1060 are the
triethanolamine.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0019] These previous references fail to teach a method whereby a
sufficiently intimate mixture of the comonomers is provided such
that polymerization leads to a true copolymer with a significant
number of both aspartate and succinimide residues or the synthesis
of polysuccinimide.
[0020] A. Thermal Synthesis of Copoly(succinimide-aspartate)
[0021] A method has now been discovered providing a sufficiently
intimate mixture of the comonomers and, therefore, allowing the
production of a true copolymer with a significant number of both
aspartate (also referred to as amide) residues or units and
succinimide (also referred to as imide) units or residues, as
schematically shown by the following reaction: 1
[0022] The invention also can provide the resulting copolymers in
isolated form. By isolated form it is meant that the copolymer is
either: (a) in the substantial absence, e.g., less than 10%,
preferably less than 5%, more particularly less than 1%, by weight
of a polyaspartate or polysuccinimide homopolymer, (b) prepared by
a method defined by this invention or (c) polyaspartate and/or
polysuccinimide homopolymer from the copolymer.
[0023] Accordingly, the present invention teaches novel methods for
producing mixed amide/imide copolymers of amino acids, as well as
the resulting novel imide-containing polyamino acids themselves.
Included are methods employing the monomers aspartic acid or
aspartate salts having non-volatile or non-heat-decomposable
cations. By aspartate or aspartate salt is meant a salt of the
aspartate ion and any metallic cation, including alkali metal,
alkaline earth metals or transition metals. Preferably the cations
are alkali or alkaline earth metals, particularly Na, Mg, K, Ca,
Rb, Sr, Cs and Ba, with sodium, magnesium, potassium and calcium,
particularly sodium, being preferred. These monomers lead to amide
formation. Other monomer, particularly aspartates having a volatile
or heat-decomposable cation, preferably an ammonium or amine
cation, lead to imide formation. In the following, the
amide-generating cation will be represented by sodium (Na.sup.+)
and the imide-generating cation will be represented by ammonium
(NH.sub.4.sup.+) but with the understanding that other cations
creating the same effects for achieving the invention may be
substituted. By volatile or heat-decomposable cation it is meant
that the cation sufficiently dissociates from the aspartate anion
under the given drying conditions such that the remaining aspartate
unit can cyclize to a succinimide unit during the polymerization.
Cations which have at least 50% dissociation in this manner under
the given drying conditions are considered volatile or
heat-decomposable and cations which do not dissociate at least 50%
are considered non-volatile or non-heat decomposable.
[0024] In the present invention, some elements of the conventional,
enzymatic processes for production of aspartic acid can be adapted
for producing monomers useful in the invention. The production of
the comonomer mixture, however, is a novel aspect. The method
involves providing an intimate solution of an aspartate of a
non-volatile cation and an aspartate of a volatile cation. By the
term aspartate is meant an aspartic acid residue, either as a
monomer or as a polymerized or copolymerized unit having its
carboxyl group in ionic form associated with a cation, i.e., as
--COO.sup.-. Specifically, for example, an ammonium aspartate
solution can be titrated with NaOH to a fractional molar
equivalence of a sodium salt of aspartate and an ammonium salt of
aspartate. This comonomeric solution is then dried to produce a
comonomer mixture of a partial sodium salt of aspartic acid and
free aspartic acid. By free aspartic acid is meant aspartic acid or
a polymerized or copolymerized aspartic acid residue having its
carboxyl group not in ionic form, i.e., --COOH. Because the dried
comonomer mixture is prepared from the novel intimate solution of
comonomers, an intimate dried mixture of these comonomers is
obtained. Although not intending to be bound by this theory, it is
believed that the mixture is intimate to the extent of exhibiting a
salt lattice structure of the aspartate with the aspartic acid. It
is possible for the dried comonomeric composition to also contain
some residual ammonium aspartate, but in very small amounts, e.g.,
not exceeding 10% by weight, preferably not exceeding 5% by weight,
more preferably not exceeding 2% by weight.
[0025] In effect, the aspartate of the volatile cation (e.g.
ammonium) when dried from aqueous solution, is largely converted to
powdered or crystalline aspartic acid. This is due to the loss of
the decomposable cation, e.g., ammonia, as a vapor upon drying,
with accompanying lowering of the pH of the evaporating solution as
ammonia leaves the solution, for example, as a result of the
following equilibrium being pulled to the left:
.Arrow-up
bold.NH.sub.3NH.sub.3+H.sub.2ONH.sub.4OHNH.sub.4.sup.++OH.sup.-.
[0026] As is understood, however, by those skilled in the art, the
term "dried" does not imply the complete absence of ammonia.
Rather, the comonomer mixture might contain an amount of ammonia
which is subsequently removed during the polymerization, as
described below.
[0027] The sodium ion, on the other hand, has no significant vapor
phase during drying and remains in the dried salt as a counter ion
to aspartate monomers. Thus, the relative proportions of the
comonomers, monosodium aspartate and aspartic acid, is set by the
relative molar amounts of ammonium aspartate in solution and the
NaOH added to the solution prior to drying.
[0028] The dried comonomer mixture is a clear, glassy solid at room
temperature if drying occurs in vacuo or in an oxygen-depleted
atmosphere. In the presence of atmospheric oxygen, the dried
comonomer preparation has a pale yellow, glassy appearance.
[0029] The comonomer composition of the present invention may also
be prepared via non-enzymatic, chemical production of solutions of
ammonium aspartate. For example, maleic acid plus ammonia in water
plus heating, preferably at an elevated pressure, may produce
ammonium aspartate in solution. Typically, temperatures of 80 to
160.degree. C., preferably 120 to 160.degree. C. and a pressure of
up to about 120 psi can be used, although other conditions may be
useful depending on the particular circumstances. Upon addition of
the desired amount of NaOH, this solution is dried to form the
comonomer composition containing the mixture of the sodium
aspartate salt and aspartic acid.
[0030] The comonomeric composition may also be obtained via
coprecipitation from solution. For example, addition of a
hydrophobe or downward adjustment of pH may lead to coprecipitation
of the monomers. These may then be isolated, for example by
filtration, for use in the production of the imide-containing
polymers. Dewatering stage or concentration of monomers may be done
by any suitable technique including wiping film evaporator, drum
drying, evaporation in a screw reactor or inline concentrator,
etc.
[0031] Also included are methods in which maleic acid plus ammonia
plus soluble, non-alkali as well as alkali, cationic salts are used
to internally generate a combination of aspartic acid and
monosodium aspartate comonomers for thermal polymerization to
produce water-soluble, imide containing copolymers.
[0032] In an additional embodiment the polysuccinimide of the
present invention is derivatized in water in the presence of a
combination of amines, such as ammonium hydroxide in combination
with 2-aminoethanol. The resulting polysuccinimide derivative
contains a free carboxylic acid and the amides of ammonia and
aminoethanol. It is desirable in some uses to provide
polysuccinimide in the absence of a sodium salt, usually formed in
the hydrolysis of poly with sodium hydroxide. To avoid the presence
of sodium salt, in a preferred embodiment of the present invention,
the succinimide rings are hydrolyzed in the presence of a tertiary
amine to form a tertiary amine salt of polyaspartic acid. Therefore
by the proper combination of various amines, derivatives are made
from polysuccinimide exhibiting higher molecular weight, in the
order from 30,000 to 150,000 weight average including all
increments in between, and reduced color. In an additional
embodiment the polymerization is carried out in the presence of a
catalyst, such as phosphoric and polyphosphoric acid, and any
hydrogen acid.
[0033] B. Synthesis of Polysuccinimide (PSI) in a Supercritical
Fluid
[0034] In another embodiment of the present invention a method has
now been discovered allowing the production of polysuccinimide at
high molecular weight and high yield in a supercritical fluid as a
solvent. A supercritical fluid is a fluid medium that is at a
temperature that is sufficiently high that it cannot be liquified
by pressure. A supercritical fluid relates to dense gas solutions
with enhanced solvation powers, and can include near supercritical
fluids. The basis for a supercritical fluid is that at a critical
temperature and pressure, the liquid and gas phases of a single
substance can co-exist.
[0035] Further, supercritical fluids are unique states of matter
existing above certain temperatures and pressures. As such, these
fluids exhibit a high level of functionality and controllability
that can influence not only the macrophysical properties of the
fluid, but also influence nano-structures of molecules dissolved in
them.
[0036] The supercritical fluid phenomenon is documented, for
example, in the CRC Handbook of Chemistry and Physics, 67th
Edition, pages F-62 to F-64 (1986-1987), published by the CRC
Press, Inc., Boca Raton, Fla. At high pressures above the critical
point, the resulting supercritical fluid, or "dense gas", attains
densities approaching those of a liquid and assumes some of the
properties of a liquid. These properties are dependent upon the
fluid composition, temperature, and pressure. As used herein, the
term "critical point" denotes the transition point at which the
liquid and gaseous states of a substance merge with each other and
represents the combination of the critical temperature and critical
pressure for a given substance.
[0037] The compressibility of supercritical fluids is great just
above the critical temperature where small changes in pressure
result in large changes in the density of the supercritical fluid.
The "liquid-like" behavior of a supercritical fluid at higher
pressures results in greatly enhanced solubilizing capabilities
compared to those of the "subcritical" compound, with higher
diffusion coefficients and an extended useful temperature range
compared to liquids. It has also been observed that as the pressure
increases in a supercritical fluid, the solubility of the solute
often increases by many orders of magnitude with only a small
pressure increase.
[0038] Near-supercritical liquids also demonstrate solubility
characteristics and other pertinent properties similar to those of
supercritical fluids. Fluid "modifiers" can often alter
supercritical fluid properties significantly, even in relatively
low concentrations. In one embodiment, a fluid modifier is added to
the supercritical fluid. These variations are considered to be
within the concept of a supercritical fluid as used in the context
of this invention. Therefore, as used herein, the phrase
"supercritical fluid" also denotes a compound above, at, or
slightly below the critical temperature and pressure (the critical
point) of that compound.
[0039] The use of supercritical fluids in the production of
polymers as a swelling, foaming or purification agent is known from
various sources. Supercritical fluid serves to increase resin
mobility thereby improving mixing and processing, to reduce the
polymer glass transition temperature by swelling, and enabling
processing at lower temperatures, and acts as a solvent for
impurities (including unreacted monomer and residual conventional
solvents) which may be removed during the processing to give high
purity products. Moreover the fluid can be used to aerate the
polymer by transition to non-critical gaseous state whereby a
porous material may be obtained. Supercritical fluid has found
application in incorporation of dyes and other inorganic materials
which are insoluble in the supercritical fluid, for example
inorganic carbonates and oxides, into polymers with a good
dispersion to improve quality, in particular dispersion in products
such as paints for spray coating and the like.
[0040] Accordingly, in another embodiment of the present invention
an additive is dispersed into the polysuccinimide or
copoly(succinimide-aspa- rtate) or a derivative thereof formed in a
supercritical fluid.
[0041] Examples of compounds which are known to have utility as
supercritical fluids are, but are not limited to, CO.sub.2,
NH.sub.3, H.sub.2O, N.sub.2O, xenon, krypton, methane, ethane,
ethylene, propane, pentane, methanol, ethanol, isopropanol,
isobutanol, CClF.sub.3, CFH.sub.3, cyclohexanol, CS.sub.2, and a
mixture thereof.
[0042] Due to the low cost, environmental acceptability,
non-flammability, and low critical temperature of carbon dioxide,
nitrous oxide, and water, supercritical carbon dioxide, nitrous
oxide and/or H.sub.2O fluid is preferably employed in the present
invention. More preferably carbon dioxide is employed in the
present invention.
[0043] In another embodiment of the present invention, a cosolvent
is preferably used in conjunction with the supercritical fluid as a
polymerization vehicle. Suitable cosolvents include, but are not
limited to, trans-2-hexenyl acetate, ethyl trans-3-hexenoate,
methyl caproate, isobutyl isobutyrate, butyl acetate, butyl
methacrylate, hexyl acetate, butyl butyrate, pentyl propionate,
methyl ethanoate, ethyl caproate, methyl dodecanoate, 2-ethylbutyl
acetate, methyl oleate, dodecyl acetate, methyl tridecanoate,
soybean oil methyl esters, hexane, heptane, tetradecane,
hexadecane, toluene, 1-hexadecene, 1-dodecanol, 1-nonanol, methyl
alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, allyl
alcohol, n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol,
t-butyl alcohol, n-amyl alcohol, isoamyl alcohol, t-amyl alcohol,
n-hexyl alcohol, cyclohexanol, n-octyl alcohol, octanol-2, n-decyl
alcohol, lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl
alcohol, benzyl alcohol and a mixture thereof.
[0044] The supercritical fluid is preferably maintained at a
pressure from about 500 psi to about 2500 psi, more preferably from
about 700 psi to about 2000 psi, and at a temperature from about
50.degree. C. to about 300.degree. C., more preferably from about
100.degree. C. to about 250.degree. C. The term "about" is used in
the present application to denote a variation of 10% of the stated
value.
[0045] The weight percentage of cosolvent and solute in the
supercritical fluid is preferably from about 1% to about 20%, more
preferably from about 5% to about 15%.
[0046] The weight average molecular weight of the polysuccinimide
in accordance with the above process is in the order of from about
2,000 to about 10,000 Dalton, including all increments within that
range, and preferably in the order of from about 3,000 to about
5,000 Daltons.
[0047] In another embodiment of the present invention the
polymerization of aspartic acid to polysuccinimide in a
supercritical fluid is carried out in the presence of a catalyst,
preferably an acidic catalyst, such as phosphoric acid.
[0048] In another embodiment of the present invention, the
polymerization is carried out in the presence of a thermal
stabilizer or an antioxidant or a mixture thereof.
[0049] In an additional embodiment of the present invention, the
polymerization of aspartic acid is performed in the dispersed
phase. The term "dispersed phase" is herein used to denote a
heterogeneous mixture where the monomer particles are suspended in
the polymerization medium, where the polymerization medium forms
the continuous phase.
[0050] In accordance with the present invention, the product of the
polymerization is isolated by concentrating the polymerization
medium, in particular water, by a method such as: distillation,
screw extrusion, thin film evaporation, drum evaporation, by means
of a belt dryer, or spray drying.
[0051] C. Synthesis of Copoly(succinimide-aspartate) in a
Supercritical Fluid
[0052] In another embodiment of the present invention a
copoly(succinimide-aspartate) is synthesized in a supercritical
fluid at high molecular weight and high yield. In accordance with
this embodiment, a mixture of sodium aspartate and ammonium
aspartate is prepared in a similar manner to that discussed in the
thermal synthesis of copoly(succinimide-aspartate) above. This
mixture is then subjected to polymerization in a supercritical
fluid in a method similar to that described for the synthesis of
polysuccinimide above. The weight average molecular weight is in
the order of about 2,000 to about 10,000 Dalton, including all
increments within that range, and preferably in the order of from
3,000 to 5,000 Daltons.
[0053] In another embodiment of the present invention, the
polymerization is carried out in the presence of a thermal
stabilizer or an antioxidant or a mixture thereof.
[0054] D. Ring-Opening of Polysuccinimide to form Derivatives
[0055] The term "ring-opening" as used in this application denotes
the formation of a derivative of polysuccinimide by opening at
least one succinimide ring, as shown schematically by the following
reaction: 2
[0056] Until now derivatives such as those made from
copoly(succinimide-aspartate) have been very difficult to make. We
have discovered that polysuccinimide can be derivatized by using
combinations of amines. For example, a combination of ammonium
hydroxide and 2-aminoethanol resulted in the formation of a resin
with free carboxylic acid salts, and the amides of ammonia and
aminoethanol. Additional compounds in accordance with the present
invention include aminopyridine and imidazole.
[0057] It is sometimes preferable to have the polysuccinimide
substantially in the absence of sodium salts. The usual salts
derived from polysuccinimide hydrolysis with sodium hydroxide
result in the sodium polyaspartate. Thus, in another aspect of this
invention the succinimide rings are hydrolyzed by a tertiary amine
to form the tertiary amine salt of polyaspartic acid.
[0058] An amine in accordance with the present invention is any
amine of the general formula:
R.sub.1R.sub.2R.sub.3N
[0059] where R.sub.1, R.sub.2, and R.sub.3 are the same or
different radicals selected from a hydrogen, an alkyl, such as
methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,
t-butyl, n-amyl, isoamyl, t-amyl, n-hexyl, n-octyl, capril,
n-decyl, lauryl, myristyl, cetyl, and stearyl; substituted alkyl,
such as hydroxyethyl; alkenyl, such as allyl; aryl, such as phenyl;
aryl-alkyl, such as benzyl; or substitute aryl radical, such as
alkylphenyl, chlorophenyl and nitrophenyl.
[0060] Further, a polyamine, such as a diamine, a triamine, a
protein, a peptide, a gelatin, chitin, lysine, ornithine, or a
melamine, can be used to provide additional sites for further
reactions. An example of the latter is to open the succinimide ring
with an aminoalcohol, such as a diethanolamine, to provide a
polyfunctional OH group-containing resin to further react. A
further example is to open all the succinimide rings with
sufficient diamine, such as hexamethylene diamine, so that no
crosslinking can occur but that each amide formed has an amine
group at the end. Thus, chemistry can be performed on that amine
group, such as a reaction with a polyfunctional isocyanate to chain
extend the imide-containing polyamino acid or to form a crosslinked
gel. An aminoethoxylate can be used to form a polymer with a long
chain ethoxylate. Also, an aminoethoxylate containing a hydrophobic
end group can be used to form a rheology modifier or an associative
thickener. An additional amino functional material can be used to
react in a nucleophilic addition with the imide-containing
polyamino acid such as: an allyl. Further, amino polybutadiene and
an amino terminated fatty olefin can be used in a nucleophilic
addition with the imide-containing polyamino acid which could
achieve the same result as an allyl amine and in addition be able
to crosslink by an oxidative cure mechanism. Further, an
amino-aromatic compound, such as aniline or a substituted aniline
can be used in the nucleophilic addition in accordance with the
present invention. Preferably, the amine is tertiary amine, more
preferably, triethanol amine.
[0061] Therefore by the proper combination of various amines,
derivatives can be made from polysuccinimide which are similar in
functionality to those made from copoly(succinimide-aspartate) but
exhibit higher molecular weight and reduced color.
[0062] The ring-opening reactions in accordance with the present
invention can be carried out either in a supercritical fluid (SCF)
or in water.
[0063] In another embodiment of the present invention, the
polymerization is carried out in the presence of a thermal
stabilizer or an antioxidant or a mixture thereof as discussed
below.
[0064] E. Polymer Additives
[0065] The polymers of the present invention may be mixed with a
number of additives during the polymerization, prior to isolation,
as described above, or post isolation. The additives are selected
to impart the desired properties to the end product and to
facilitate its fabrication. In the post isolation mixing
(compounding) of additives, it is preferred that the polymers,
copolymers or derivatives of the present invention are blended with
a material to reduce the melt viscosity of the polymers, copolymers
or derivatives of the present invention. Such materials include,
but are not limited to, a plasticizer or a polymer, other than the
polymers in accordance with the present invention, to form a
polymer blend; preferably the resulting polymer blend is
substantially a miscible polymer blend. Arriving at a specific
complex formulation may be the result of an engineering art and
experimentation. Preferred polymer additives include, but are not
limited to the following:
[0066] Stabilizers: During processing a polymer must be brought to
the molten state at temperatures much above those of their melting
or glass transition. This is done to lower their viscosity and to
extend the upper limit of possible processing rates without melt
fracture. Consequently there is the real danger of thermal
degradation during processing. For this reason heat stabilizers,
such as free radical scavengers, maybe used. Polymer chains maybe
also sensitive to forms of energy other than thermal. In
particular, uses that are intended for outdoor applications must be
able to withstand ultraviolet (UV) radiation, for which purpose UV
stabilizers are added. In addition the polymer maybe stabilized
against oxidative degradation, both short term at elevated
processing temperatures, and long term during storage and use. In
an oxidative degradation oxygen is absorbed and produces free
radicals that react with the chains, usually autocatalytically, and
degrade them. Most of the antioxidants combine with the
oxygen-generated free radicals and inactivate them.
[0067] Antioxidants: Antioxidants are chemical compounds which are
incorporated at low concentrations into polymer systems to retard
or inhibit polymer oxidation and its resulting degradative effects
by atmospheric oxygen. Their use is essential in order to protect
the polymer during production, processing, compounding, and end
use. Oxidation is a common natural phenomenon which can occur at
any phase of a polymer's existence: during polymerization,
processing, or end use of the product. The process may cause a
variety of chemical and physical changes such as discoloration,
loss of gloss or transparency, surface chalking and cracks.
Oxidation tends to lower the physical properties of a polymer, such
as impact strength, elongation, and tensile strength. The process
may continue to degrade a polymer article until it loses its
utility. The rate and effects of oxidation differ depending on the
polymer, manufacturing process, and morphology.
[0068] Auto-oxidation: Organic materials react with molecular
oxygen in a process called "auto-oxidation". Auto-oxidation is a
free-radical chain reaction and, therefore, can be inhibited at the
initiation and propagation steps. The process is initiated when
free alkyl radicals (R.multidot.) are generated in the polymer by
heat, radiation, stress, or residues. Without the protection
afforded by antioxidants, these radicals begin a chain reaction
which degrades the polymer.
[0069] Although Applicants do not wish to be bound to any
particular theory, it is generally believed that polymeric
oxidation begins when a free radical containing a highly reactive
electron reacts with oxygen forming peroxy radicals
(ROO.multidot.). These react with the polymer to produce
hydroperoxides (ROOH) which decompose further to form two new free
radicals. These begin the cycle anew, propagating a cascade of
reactions that, sometimes in the absence of an antioxidant, can
turn into a chain reaction leading to the failure of the polymer.
Antioxidants terminate this sequence and eliminate free radicals
from the system. Stabilization is achieved either by termination
reactions or by inhibiting the formation of free radicals. Primary
antioxidants increase the number of terminations while secondary
antioxidants reduce the formation of free radicals. Primary and
secondary antioxidants are often used together with synergistic
results.
[0070] Primary antioxidants: Primary antioxidants such as hindered
phenols and secondary arylamides interrupt free radical processes
by donating labile hydrogen atoms to change propagating hydroperoxy
radicals into stable species.
[0071] Hindered phenols: Hindered phenols interrupt the
auto-oxidation cycle. The hindered phenol is capable of donating
hydrogen atoms, undergoing rearrangement reactions, and further
reacting with free radicals until it is fully consumed.
Over-oxidation of the hindered phenol is undesirable since it
causes discoloration. Several approaches to stabilization which
avoid over-oxidation of the phenolic have been developed. Trivalent
phosphorous compounds and antacids(calcium stearate and zinc
stearate) to scavenge acidic catalyst residues are typically used
as co-additives in combination with the phenolic. Most of the newer
commercial antioxidants are of this type, such as alkylated
hydroquinones and phenols. In high temperature applications,
polynuclear phenols generally are preferred over monophenols
because of their lower sublimation rates. Phenolic antioxidants are
typically used at levels ranging from 0.05 to 2.0 wt %.
[0072] Amines: The ability of amines, preferably aromatic amines,
to stabilize at high temperature makes them useful in applications
requiring prolonged exposure to elevated temperatures. Amines can
be classified further as ketone-amine condensation products,
diaryldiamines, diarylamines, and ketone-diarylamine condensation
products. Both solid and liquid products are marketed. Typical use
levels are 0.5 to 3%.
[0073] Secondary antioxidants: Secondary antioxidants, such as
phosphites or thioesters, are peroxide decomposers that undergo
redox reactions with hydroperoxides to form stable products. They
are cost effective because they can be substituted for a portion of
the more costly primary antioxidant and provide equivalent
performance.
[0074] Phosphites: Phosphites generally are used in combination
with other antioxidants, particularly phenols, the most commonly
used secondary antioxidants, reduce hydroperoxides to alcohols.
Phosphites are highly effective process stabilizers,
nondiscoloring, and have broad FDA regulation for many indirect
food contact applications. Tri (mixed nonyl- and dinonylphenyl)
phosphite is used in the largest volume. Use levels vary from 0.05
to 3.0 wt %.
[0075] Thioesters: Thioesters reduce hydroperoxides to alcohols.
Thioesters are nondiscoloring, FDA regulated, and incorporated to
improve long-term heat stability. Typical use levels are from 0.1
to 0.3 wt % in polyolefins with higher levels used in polymers
containing unsaturation.
[0076] Synergy between primary and secondary antioxidants:
Combinations of certain antioxidants sometimes provide synergistic
protection. The most common synergistic combinations are mixtures
of antioxidants operating by different mechanisms. For example,
combinations of peroxide decomposers may be used with propagation
inhibitors. Similarly, combinations of metal chelating agents maybe
used with propagation inhibitors. Synergistic combinations of
structurally similar antioxidants are also known, particularly
combinations of phenols.
[0077] Blends of a phenolic and a phosphite are very useful for
melt compounding. They work well to maintain the molecular weight
of the polymer, while at the same time maintaining low color. The
phosphite decomposes hydroperoxides and protects the phenolic
during processing thereby preventing (if optimum levels of both are
added) over-oxidation of the hindered phenol and inhibiting the
formation of colored by-products. This preserves the phenolic for
long term thermal stability. Blends of the phenolic antioxidant and
a thioester are a good combination for long term thermal stability
of the polymer.
[0078] Two main classes of antioxidants inhibit the initiation step
in thermal auto-oxidation. The peroxide decomposers function by
decomposing hydroperoxides through polar reactions. Metal
deactivators are strong metal-ion complexing agents that inhibit
catalyzed initiation through reduction and oxidation of
hydroperoxides. The most important commercial propagation
inhibitors are hindered phenols and secondary alkylaryl- and
diarylamines.
[0079] Additional antioxidants include:
[0080] Sulfides: Dilauryl thiodipropionate and distearyl
thiodipropionate are the most important commercial antioxidants in
this class. They are used with phenols to give synergistic
combinations.
[0081] Metal salts of dithioacids: These substances act as
hydroperoxide decomposers and propagation inhibitors, and are used
in conjunction with other antioxidants, particularly phenols.
[0082] Bound antioxidants: Recently, antioxidants have been
developed that are copolymerized into the polymer chain. The main
advantage of such a system is low antioxidant extractability in
applications where the polymer is in contact with solvents capable
of extracting conventional antioxidants.
[0083] Additional additives include:
[0084] Colorants: Preferably, for decorative reasons, colorants
such as pigments and dyes that absorb light at specific wavelengths
are added to the polymers of the present invention.
[0085] Plasticizers: The term "plasticizer" stems from the process
of making the polymer more susceptible to plastic flow.
[0086] Plasticizers, preferably external plasticizers, are usually
monomeric molecules that when mixed with polar or hydrogen bonded
polymers, position themselves between these intermolecular bonds
and increase the spacing between adjacent bonds. Of course they
must also either be polar or be able to form hydrogen bonds. The
result of this action is to lower the level of the strength of
intermolecular forces, thus decreasing the mechanical strength and
increasing the flexibility of the rigid structure. The plasticizer
may preferably be introduced to the polymer by copolymerization. In
this context copolymerization is sometimes referred to as internal
plasticization.
[0087] Reinforcing Agents: This category of additives is very broad
and yet very important in that such additives improve the
mechanical properties of the base polymers, chiefly their strength
and stiffness. Short and long glass fibers, graphite fiber are
common additives in applications calling for improved mechanical
properties, including the absence of creep (dimensional stability).
Solid reinforcing agents also extend the upper temperature limit of
the use of the base polymer.
[0088] Fillers: The main function of fillers is to reduce the cost
of the end product. A very inexpensive filler, occupying a fraction
of the volume of a plastic article, will have such an economic
benefit. Nevertheless, fillers are also often specialty additives;
they may be present to reduce the thermal expansion coefficient of
the base polymer, to improve its dielectric properties, or to
"soften" the polymers (e.g., calcium carbonate).
[0089] Lubricants: Lubricants are very low concentration additives
that are mixed with polymers to facilitate their flow behavior
during processing. There are two categories of lubricant, external
and internal. External lubricants are incompatible at all
temperatures with the polymer they are used with; therefore during
processing they migrate to the melt-metal interface, promoting some
effective slippage of the melt by reducing interfacial layer
viscosity. Internal lubricants, on the other hand, are polymer
compatible at processing temperatures, but incompatible at the use
temperature. Therefore, during processing they reduce
chain-to-chain intermolecular forces, thus melt viscosity. As the
processed plastic products cool, they become incompatible (phase
separation) and can eventually migrate to the surface; thus product
properties are not permanently affected.
[0090] In an additional embodiment in accordance with the present
invention, the polysuccinimide, a copolymer or a derivative thereof
is processed in a processing equipment. The processing of polymers
is discussed extensively in Principles of Polymer Processing by R.
T. Fenner, Chemical publishing (1979) and Principles of Polymer
Processing, by Z. Tadmor et al, John Wiley & Sons, New York,
(1979) both of which are incorporated herein by reference.
Following are some aspect concerning the processing of the
materials of the present invention:
[0091] F. Processing
[0092] The materials of the present invention can be further
processed by one of the principal methods used to process
thermoplastic materials into finished or semifinished products,
namely, screw extrusion, injection molding, blow molding and
calendering. An important distinction exists between extrusion and
calendering on the one hand, and molding techniques on the other,
in that while the former are continuous processes, the latter are
discontinuous. The term "materials of the present invention" is
used to denote polysuccinimide, copoly(succinimide-aspartate), a
derivative thereof and a blend thereof with an additive.
[0093] Screw Extrusion: In an embodiment in accordance with the
present invention the materials of the present invention are
extruded. The extrusion process is used to shape a molten polymeric
material into a desired form by forcing it through a die. A variety
of profiles can be formed in a continuous extrusion which include,
but are not limited to, filaments, films and sheets. The required
pressure is generated by at least one rotating screw in a heated
barrel as shown in FIG. 1. While the form of the die determines the
initial shape of the extrudate, its dimensions may be further
modified, for example, by stretching, before final cooling and
solidification takes place. A screw extruder may also be used, in
accordance with the present invention, to further react the
polyimide of the present invention by means of introducing a
reactant in the extruder through an injection port as shown in the
Figure. The segments of the extruder can be separately heated to
different temperatures. Further, the position of the injection port
can be moved to a different location along the screw of the
extruder to facilitate different residence time and reaction time
of the reactant within the extruder. It is also possible to add
additional injection ports to facilitate the addition of different
reactants that require different residence time in the extruder in
order to facilitate to desired reaction.
[0094] Single-screw Extrusion: The Figure shows the diagrammatic
cross-section of a typical single-screw extruder, which is used to
melt and to pump the polymer. Solid material in the form of either
granules or powder is usually gravity fed through the hopper,
although crammer-feeding devices are sometimes used to increase
feed rates. The channel is relatively deep in the feed section, the
main functions of which are to convey and compound the solids.
Melting occurs as a result of the supply of heat from the barrel
and mechanical work from the rotation of the screw.
[0095] The screw is held in position by an axial thrust bearing and
driven by an electric motor via a reduction gearbox. Screw speeds
are generally within the range of from 50 to 150
revolutions/minute, and it is usually possible to vary the speed of
a particular machine over at least part of this range.
[0096] Barrel and die temperatures are maintained by externally
mounted heaters, typically of the electrical-resistance type.
Individual heaters or groups of heaters are controlled
independently via thermocouples sensing the metal temperatures, and
different zones of the barrel and die are often controlled at
different temperatures. The region of the barrel around the feed
pocket is usually water cooled to prevent fusion of the polymer
feedstock before it enters the screw channels. Cooling may also be
applied to part or all of the screw by passing water or other
coolant through a passage at its center, access being via a rotary
union on the driven end of the screw.
[0097] The size of an extruder is defined by the nominal internal
diameter of the barrel. Sizes range from about 25 mm for a
laboratory machine, through 60-150 mm for most commercial product
extrusions, up to 300 mm or more for homogenization during polymer
manufacture. Common thermoplastic extruders have screw
length-to-diameter ratios of the order of 25 or more. An important
characteristic of a screw is its compression ratio, one definition
for which is the ratio between channel depths in the feed and
metering sections. This ratio normally lies in the range of from 2
to 4, according to the type of material processed. Output rates
obtainable from an extruder vary from about 10 kg/h for the
smallest up to 5000 kg/h or more for the largest homogenizers.
Screw-drive power requirements are usually of the order of 0.1-0.2
kW h/kg.
[0098] Many modifications to the basic form of screw design can be
used, often with the aim of improving mixing. Another variant is
the two-stage screw, which is effectively two screws in series. The
vent of the melt at the end of the first stage, where the screw
channel suddenly deepens, makes it possible to extract through a
vent any air or volatiles trapped in the polymer.
[0099] Multiscrew Extrusion: In addition to single screw extruders,
there are twin and multiscrew extruders performing substantially
the same functions, twin-screw machines being the most common. Such
extruders can have two screws intermeshing or not quite
intermeshing, corotating or counter rotating. The more common
intermeshing type have distinct advantages over single-screw
machines in terms of an improved mixing action, and are not so much
screw viscosity pumps as positive displacement pumps.
[0100] Extrusion Dies: The simplest extrusion dies are those used
to make axisymmetric products such as lace and rod. The main design
consideration with such dies is that changes in flow channel
diameter from that of the extruder barrel bore to that of the die
exit are gradual. Smooth melt flow is thus ensured, with no regions
where material can be retained and degraded. In designing dies for
more complicated profiles, due allowance must also be made for
elastic recovery, which may cause changes in shape after the
extrudates leave the dies. Other types of extrusion die are used in
the production of flat film, sheet, pipe and tubular film, and in
covering wire and cable.
[0101] Flat-film and Sheet Extrusion: The distinction between flat
film and sheet is one of thickness, both being extruded in similar
types of dies. As the widths of such flat sections are much greater
than the extruder-barrel diameters, the dies must spread the melt
flow laterally and produce extrudates of as uniform a thickness as
possible.
[0102] Pipe, Tube and Profile Extrusion: Pipe, tube and profile
extrusion process is another extrusion operation. Pipes and tubes
are usually distinguished by size. Below 1.25 cm (0.5 in) diameter
is called a tube; above 1.25 cm (0.5 in) diameter is called a
pipe.
[0103] Wire and Cable Covering: Wire and cable covering operations
are carried out over a very wide range of line speeds, from about 1
m/min for large high-voltage electrical cables to 1000 m/min or
more for small-diameter wires. Nevertheless, the types of die used
are similar, being of the crosshead type to accommodate the
conductor entering at an angle--often a right angle--to the axis of
the extruder. The success of such an arrangement depends on the
design of the flow deflector, which serves to distribute the melt
into a layer of uniform thickness on the conductor.
[0104] Injection Molding: The term "injection molding" as used
herein denotes the process for producing substantially identical
articles from a hollow mold. In the injection molding process,
molten polymer is forced under high pressure into a closed mold of
the required shape, where it is cooled before the mold is opened
and the finished article extracted.
[0105] Blow Molding: Blow molding is used for the formation of
hollow articles, such as bottles and other containers, manufactured
by the blow molding process. The blow molding process involves
first the formation of a molten parison, which is a preshaped
sleeve, usually made by extrusion. Air is blown into the parison
surrounded between two mold halves expending the parison and
causing it to take the shape of the mold. The polymer solidifies
and the hollow article is ejected.
[0106] Calendering: The term "calendering" as used herein denotes a
process for producing continuous films or sheets by pressing molten
polymer between rotating rolls.
[0107] Another process that is very important for the production of
fibers and filaments is that of spinning. Melt supplied by either
an extruder or gear pump is forced vertically downwards through a
series of very small holes in a flat plate or spinneret, and the
resulting threads are air cooled and rapidly stretched by winding
at high speed on to a bobbin.
[0108] Further, the polymers and copolymer of the present invention
can be worked by engineering techniques including welding, cutting
and machining, although to do so to any significant extent is to
lose the advantage offered by polymeric materials over metals in
terms of ease of fabrication.
[0109] Having generally described this invention, a further
understanding can be obtained by reference to certain specific
examples which are provided herein for purposes of illustration
only and are not intended to be limiting unless otherwise
specified.
EXAMPLES
1. The Triethanolamine Salt of Polyaspartic Acid from
Polysuccinimide (PSI)
[0110] To 5 grams (51.5 mEq of succinimide residues) of
Polysuccinimide (MW=34,500 Daltons) was added 7.74 grams (51.9 mEq)
of Triethanolamine and 23.34 grams of double distilled water. This
dispersion was placed into an oven at 80.degree. C. with a magnetic
stirrer for 29 hours. The solution was reddish and had some
residual solids which were filtered out (note: this sample of PSI
when hydrolyzed with NaOH also has residual solids).
1TABLE 1 Results of the Titration Filtrate Measured Theoretical
Species (mEq/g solids) (mEq/g solids) COOH 3.34 3.73 Amine 4.95
3.76
[0111] Therefore the degree of hydrolysis is 89.5% with remaining
excess of 31.6% amine.
[0112] The FTIR spectrum of another sample, treated with excess
triethanolamine is shown in FIG. 2. As seen there is no peak at
1710 wave numbers where the succinimide ring absorbs. The peak at
1577 is for the amide backbone, while the peak at 1386 is for the
carboxylate group. The strong peaks at 1030-1060 are the
triethanolamine.
[0113] This was repeated on a larger scale:
[0114] 41.4 g of PSI (426 mEq of succinimide residues)
[0115] 65.3 g of triethanolamine (438 mEq of triethanol amine
(TEOHA))
[0116] 65.4 g of water
[0117] The dispersion was placed into an 80.degree. C. oven, with
magnetic stirring, for overnight. The next morning the solution was
clear, reddish, and viscous. Total solids (TS) was 66.05%.
2TABLE 2 Titration Results Measured Theoretical Species (mEq/g
solids) (mEq/g solids) COOH 3.23 3.73 Amine 4.04 3.83
[0118] Therefore the degree of hydrolysis is 86.6% with remaining
excess of 5.5% amine.
[0119] 1. Derivatization of Polysuccinimide (PSI)
[0120] Polysuccinimide was treated with a varying relative amounts
of ammonia/2-aminoethanol in water. Solutions of ammonia and
2-aminoethanol were prepared and solid PSI added as shown in Table
3:
3TABLE 3 Solutions of ammonia and 2-aminoethanol 100% 65% 32% 0%
Ammonia Ammonia Ammonia Ammonia Ingredient amount mEq amount mEq
amount mEq amount mEq Concentration of 2.94 ml 51.5 1.91 ml 33.4
0.94 ml 16.5 0 ml 0 Ammonia 2-aminoethanol 0 g 0 1.1 g 18.0 2.14 g
35.1 3.14 g 51.5 Water 22 ml 22 ml 22 ml 22 ml PSI 5 g 51.5 5 g
51.5 5 g 51.5 5 g 51.5
[0121] The dispersions were placed into an 80.degree. C. oven, with
magnetic stirring for 2 hours. The dispersions changed into bright
yellow solutions within 1 hour. Total solids (TS) were determined
and the solutions were titrated and presented in Table 4.
4TABLE 4 Total solids (TS) 100% 65% 32% 0% Ammonia Ammonia Ammonia
Ammonia % TS 21.170 23.860 26.056 28.132 COOH Titer 4.407 4.073
3.733 3.392 mEq/g
[0122] The titer expected for an ammonia salt of poly(aspartic
acid) is 7.576 mEq/g. The calculated titer for a 50% ammonia
salt/50% ammonia amide is 4.065. The calculation for all the
mixtures is presented in Table 5.
5TABLE 5 Measured and Calculated COOH Groups Titer mEq/g 100% 65%
32% 0% Ammonia Ammonia Ammonia Ammonia Measured 4.407 4.073 3.733
3.392 Calculated 4.065 3.826 3.624 3.448
[0123] This demonstrates that derivatization by the amines/ammonia
to form amides has taken place but also that water competes with
the amines/ammonia for the succinimide ring so that more than 50%
of the succinimide rings are hydrolyzed to form the carboxylic acid
salt of the amines rather than forming the amides.
[0124] Inspection of the FTIR of ethanolamine shows a peak at 1067
wavenumbers. This peak is not in the sample with 100% ammonia and
is shown to grow as the ammonia level in the system decreases and
the aminoethanol level increases.
2. Additional Derivatization of Polysuccinimide (PSI)
[0125] In this example the t-amine, triethanolamine, is used in
conjunction with 2-aminoethanol to form a copolymer of aspartate
and the triethanolamine aspartate amide.
6TABLE 5 Solution of water, 2-aminoethanol and triethanolamine
Ingredients Weight (grams) Total mEq Water 137 2-Aminoethanol 15.7
257.7 Triethanolamine 36.5 257.7 Polysuccinimide 50 515.5 of
succinimide residues
[0126] The amines are dissolved in the water and the solid
polysuccinimide is added, with magnetic stirring, to the solution.
The resulting dispersion is placed into an 80.degree. C. oven, with
magnetic stirring, overnight.
[0127] The product was titrated with the following results:
[0128] COOH Titer: 383.0 mEq (therefore there are 132.5 mEq as
Amide)
[0129] "NH" Titer: 387.9 mEq (since there are 257.7 mEq of t-amine
there are 130.2 mEq of 2-aminoethanol remaining).
[0130] Thus there are 127.5 mEq of 2-aminoethanol present as the
aspartate amide in the copolymer, which is close to the amount
calculated from the COOH titer.
[0131] Obviously, numerous modifications and variations of the
present invention are possible in light of the above teachings. It
is therefore to be understood that within the scope of the appended
claims, the invention may be practiced otherwise than as
specifically described herein.
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